1. Field of the Invention
The present invention relates to an end bearing of a oneway clutch apparatus for constituting an automatic transmission, or the like, for a motor vehicle and a oneway clutch apparatus employing this end bearing, and more specifically, to a technology for preventing problems such as seizure while enhancing the productivity and reducing the manufacturing cost.
2. Related Background Art
Generally, an automatic transmission for a motor vehicle is provided with a planetary gear transmission mechanism of three to five speed levels, apart from a torque inverter serving as a fluid joint, and changes the speed by appropriately fixing or releasing the constituent elements (a sun gear, a planetary gear, etc.) of the planetary gear transmission mechanism by means of a frictional engagement means such as a clutch or a brake. As the frictional engagement means to be incorporated in the automatic transmission, a wet type multiple disc clutch is employed in which a friction plate and a separator plate are alternately provided, except in some transmissions of a band brake type. A pressure oil from a transmission control hydraulic circuit is employed for pressure contact (frictional engagement) between the both plates. As these frictional engagement means, a member which attains easier transmission control by incorporating the oneway clutch apparatus therein and freely rotating a gear shaft, etc., in one of the directions of rotation is employed in some cases.
In the oneway clutch apparatus, in order to ensure an operation of the clutch constituent elements such as a sprag, an annular end bearing 39 for restricting the movement of the clutch constituent elements, as shown in FIG. 5 or FIG. 6, is often interposed between an inner ring 5 and an outer ring 7. Normally, the end bearing 39 is formed of copper alloy (phosphor bronze or the like) or bimetal (which is obtained by bonding a copper alloy and a steel plate together as a unitary structure). For example, an end bearing shown in FIG. 5 is formed of solid blank by cutting work and that shown in FIG. 6 is formed of a plate by press work.
Out of the end bearings 39 described above is, the one formed by cutting work is excellent in performance with high accuracy and high strength, though disadvantageously requiring high processing cost with low material yield and low mass productivity. On the other hand, the one formed by press work has no such drawback or problem of the former type end bearing. However, it is difficult to enhance the strength or rigidity of this end bearing since the thickness of a plate serving as the material thereof can not be increased freely. For this reason, in a oneway clutch apparatus of an inner ring driving type, for instance, as shown in FIG. 7, if an external force is applied on the sliding-contact flange 41, a wedge-like gap 61 is generated between the flange 41 and the inner ring 5 owing to elastic deformation, so that seizure or scoring may be caused by a rise of the surface pressure in a contact portion or by break of oil film in the gap 61.